Machines for compression molding closure shells, or for compression molding sealing liners within closure shells, typically include a turret or carousel that rotates around a vertical axis. A plurality of molds are provided around the periphery of the carousel in the form of male and female mold sections that are aligned along vertical axes parallel to the axis of rotation. The mold sections are driven between an open position in which a molded part is stripped from the male mold section and a charge of plastic material is placed in the female mold section, and a closed position in which the male and female mold sections are brought together to compression mold the part. In a machine that molds closure shells, charges of plastic material are placed directly into a female mold cavities. In a machine for molding sealing liners, premade closure shells are placed in a nest when the mold sections are open, and a charge of material for the liner is placed within the shell either before or after each shell is placed in the nest. U.S. patents that illustrate machines of this type for compression molding plastic closure shells include U.S. Pat. Nos. 5,670,100, 5,989,007, 6,074,583 and 6,478,568. U.S. patents that illustrate machines of this type for compression molding sealing liners within closure shells include U.S. Pat. No. 5,451,360.
In some instances, the molten plastic charge has been propelled or “thrown” onto the molding surface in a mold cavity, which can lead to inconsistent placement of the mold charge within the cavity. This can result in diminished part quality, and operating issues including increased complexity of the delivery apparatus and mold charge placement apparatus, and difficulties with missed delivery of the pellet charge or delivery wherein only a portion of the pellet is received within the mold cavity. Other systems have required an individual cutter for every molding position or cavity, and this adds significantly to the capital, manufacture and maintenance costs and the overall complexity of the system and its controls.
The present disclosure involves a number of aspects or inventions, which may be implemented separately from or in combination with each other.
An apparatus for placing a mold charge into a cavity (e.g., either a mold cavity or the cavity of a premade closure shell), in accordance with a first aspect of the present disclosure, includes a pair of hubs mounted for rotation around parallel axes, a link connected between the hubs at positions off-center relative to the parallel axes and a blade connected to the link. Rotation of the hubs causes the blade to travel in an elliptical path relative to an extrusion orifice to cut mold charges from the orifice and place the mold charges into cavities passing beneath the blade. The apparatus preferably includes a drive member that simultaneously rotates both of the hubs to drive the blade relative to the extrusion orifice and cavities. The blade preferably includes an arm that extends into a cavity to place a mold charge into the bottom of the cavity for consistent and accurate placement of the mold charges from one cavity to the next. The link may be connected to each hub at a different distance relative to the axes of the hubs and may be adapted to pivot or rotate relative to the axes of rotation of the hubs as the hubs are rotated. Further control of the path of the blade may be accomplished by phased rotation of the hubs relative to each other to vary the path of travel of the blade.